/* The following is the NetBSD libc qsort implementation modified in order to
 * support partial sorting of ranges for Redis.
 *
 * Copyright(C) 2009-2012 Salvatore Sanfilippo. All rights reserved.
 *
 * The original copyright notice follows. */


/*	$NetBSD: qsort.c,v 1.19 2009/01/30 23:38:44 lukem Exp $	*/

/*-
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>

static inline char *med3(char *, char *, char *,
                         int (*)(const void *, const void *));

static inline void swapfunc(char *, char *, size_t, int);

#define min(a, b)    (a) < (b) ? a : b

/*
 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 */
#define swapcode(TYPE, parmi, parmj, n) {        \
    size_t i = (n) / sizeof (TYPE);        \
    TYPE *pi = (TYPE *)(void *)(parmi);        \
    TYPE *pj = (TYPE *)(void *)(parmj);        \
    do {                        \
        TYPE    t = *pi;            \
        *pi++ = *pj;                \
        *pj++ = t;                \
        } while (--i > 0);                \
}

#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
    es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;

static inline void
swapfunc(char *a, char *b, size_t n, int swaptype) {

    if (swaptype <= 1) swapcode(long, a, b, n)
    else swapcode(char, a, b, n)
}

#define swap(a, b)                        \
    if (swaptype == 0) {                    \
        long t = *(long *)(void *)(a);            \
        *(long *)(void *)(a) = *(long *)(void *)(b);    \
        *(long *)(void *)(b) = t;            \
    } else                            \
        swapfunc(a, b, es, swaptype)

#define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)

static inline char *
med3(char *a, char *b, char *c,
     int (*cmp)(const void *, const void *)) {

    return cmp(a, b) < 0 ?
           (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a))
                         : (cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c));
}

static void
_pqsort(void *a, size_t n, size_t es,
        int (*cmp)(const void *, const void *), void *lrange, void *rrange) {
    char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
    size_t d, r;
    int swaptype, cmp_result;

    loop:
    SWAPINIT(a, es);
    if (n < 7) {
        for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
            for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                 pl -= es)
                swap(pl, pl - es);
        return;
    }
    pm = (char *) a + (n / 2) * es;
    if (n > 7) {
        pl = (char *) a;
        pn = (char *) a + (n - 1) * es;
        if (n > 40) {
            d = (n / 8) * es;
            pl = med3(pl, pl + d, pl + 2 * d, cmp);
            pm = med3(pm - d, pm, pm + d, cmp);
            pn = med3(pn - 2 * d, pn - d, pn, cmp);
        }
        pm = med3(pl, pm, pn, cmp);
    }
    swap(a, pm);
    pa = pb = (char *) a + es;

    pc = pd = (char *) a + (n - 1) * es;
    for (;;) {
        while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
            if (cmp_result == 0) {
                swap(pa, pb);
                pa += es;
            }
            pb += es;
        }
        while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
            if (cmp_result == 0) {
                swap(pc, pd);
                pd -= es;
            }
            pc -= es;
        }
        if (pb > pc)
            break;
        swap(pb, pc);
        pb += es;
        pc -= es;
    }

    pn = (char *) a + n * es;
    r = min(pa - (char *) a, pb - pa);
    vecswap(a, pb - r, r);
    r = min((size_t) (pd - pc), pn - pd - es);
    vecswap(pb, pn - r, r);
    if ((r = pb - pa) > es) {
        void *_l = a, *_r = ((unsigned char *) a) + r - 1;
        if (!((lrange < _l && rrange < _l) ||
              (lrange > _r && rrange > _r)))
            _pqsort(a, r / es, es, cmp, lrange, rrange);
    }
    if ((r = pd - pc) > es) {
        void *_l, *_r;

        /* Iterate rather than recurse to save stack space */
        a = pn - r;
        n = r / es;

        _l = a;
        _r = ((unsigned char *) a) + r - 1;
        if (!((lrange < _l && rrange < _l) ||
              (lrange > _r && rrange > _r)))
            goto loop;
    }
/*		qsort(pn - r, r / es, es, cmp);*/
}

void
pqsort(void *a, size_t n, size_t es,
       int (*cmp)(const void *, const void *), size_t lrange, size_t rrange) {
    _pqsort(a, n, es, cmp, ((unsigned char *) a) + (lrange * es),
            ((unsigned char *) a) + ((rrange + 1) * es) - 1);
}
